Red blood cells collected weekly from healthy volunteers have been used to sustain in vitro cultures of malaria parasites (Plasmodium falciparum). These organisms have been used in an array of laboratory studies. One aspect entails the in vitro evaluation of antimalarial potency of synthetic analogs of artemisinin. From these studies we have gained new insights into the molecular mechanism of action of this important class of agents. Cultures have also been used to isolate DNA and RNA from P. falciparum, to monitor the production of heat shock proteins, to infect mosquitoes, and in studies designed to evaluate vaccine candidates. Finally, these cultures were used to infect mosquitoes that were used in a study to determine whether atovaquone could prevent malaria in humans.